Nowadays, 3G or 4G networks are widely used to support high bandwidths of communication in electronic devices. However, power consumption of the electronic device increases with increase in the bandwidth. As known, the electronic device comprises a plurality of blocks. In order to comply with various specifications related to 3G & 4G standards, the complexity in arranging the plurality of blocks increases.
In electronic devices, such as mobile phones, tablets, laptops, low power consumption is desirable. In order to reduce the power consumption, each block in the electronic device is to be utilized to its fullest capacity. A variety of design techniques such as mixing blocks running on different power supply voltages, sub-threshold design, aggressive power management and various power down modes are used to overcome the difficulty in design and to reduce power consumption.
When the various blocks are running on different power supply voltages, a low voltage block can be driven by a block running on a high voltage power supply to achieve maximum input swing. The power supply voltage of the block driving the low voltage block is higher than the maximum voltage that the low voltage device can sustain without damage. In the example of a mixer, a MOSFET is used as a switch. A switch needs to have low resistance for the maximum transfer of the signal. The resistance of a MOSFET can be reduced by reducing the length. So a low voltage device is used as it can be made to have smaller length. However, the block driving the low voltage device may experience uncontrolled electrical transients, which forces the output of the block to reach as high as the power supply voltage. Further, the block driving the low voltage device may also experience controlled transients, which forces the output voltage to be greater than the maximum safe operating voltage of the low voltage device. The electrical transients generated may damage the low voltage device.
In order to protect the low voltage device, protective devices can be effectively switched into a circuit in response to a transient overvoltage, and subsequently switched out within a reasonably short period to resume normal circuit operation. In prior art, a mixer is arranged to provide a mixed signal by mixing an input signal and an oscillation signal. Usually, the control signal of the mixer switch is the oscillator signal varying over a bias voltage. The input signal is used to bootstrap the oscillator signal. Therefore, the control signal is the oscillator signal varying over the input signal. However, the mixer does not provide protection to the electronic devices during power ON and power OFF and other uncontrolled transients. Further, complexity of the circuitry in the prior art adds additional load to the high frequency clocks.